Fuel injection pump



May 24, 1938. G. J. TRAPF; A 2,118,578-

FUEL INJECTION PUMP Filed 'Aug. 15; 1935 3 Sheets-Sheet 1 INVENTOI? GLJ.Trap o.

May 24, 1938. G. J. TRAPP FUEL INJECTION PUMP Filed Aug. 15', 1935 3Sheets-Sheet 2 .May 24, 1938. s. J. TRAPP FUEL INJECTION PUMP Filed Aug.15, 1935 a Sheets-Sheet 5 [Inf/V701? 'earye J Trap 0. .5 7

I M Jifys Patented May 24, 1938 UNITED STATES PATENT OFFICE FUELINJECTION PUIWP ited, London, England Application August 15, 1935,Serial No. 36,413 In Great Britain August 16, 1934 2 Claims.

This invention relates to fuel injection pumps for internal combustionengines, and more particularly to fuel injection pumps having a workingplunger or piston of constant stroke reciprocating in a sleeve orcylinder which communicates through anon-return valve with the injectionnozzle; the beginning and end of the injection period are determined bycontrol grooves or the like, formed upon the plunger and cooperatingwiththe fuel-admission and return or release ports in the cylinder wall, oneof the grooves being provided with a helical or inclined edge forvarying the point of opening of the respective port by relative rotationof the pump plunger and cylinder.

It is one object of the present invention to provide an improvedconstruction of fuel injection pump which is simple to manufacture, andwhich provides two independent controls, for

varying on the one hand the quantity of fuel injected per stroke, and onthe other hand the timing of the injection.

It is a further object of the invention to provide an improvedconstruction in which the timing of the injection is adjusted by movinga cylinder sleeve axially, the arrangement being such that axialmovement of the sleeve does not change the volume of the compressionspace, so that movement of the sleeve can be rendered extremely light,thus simplifying the governing arrangements which are usually associatedwith fuel injection pumps. The invention further provides an improvedarrangement in which the usual cylinder and reciprocating plunger, to-

gether with those parts associated therewith, can be withdrawn readilyas a single unit, thus facilitating examination and assembly, bothbefore and after the pump is put into service.

It is a still further object of the invention to provide an improvedport construction in the reciprocatory plunger and cylinder, said portsbeing. formed with comparatively long controlling edges which serve toproduce rapid opening and closing, and which avoid the constrictingtendency which is experienced when the ports in the plunger and/ or thecylinder are circular in shape.

Another object of the invention is to provide an improved inlet andspill passage arrangement in which the fuel rejected by thereciprocatory plunger after the point of cut-off is reached,

is delivered into a channel or passageway separate from the inletpassage serving the pump, the rejected fuel thus having an opportunityof becoming de-aerated before it is returned to the inlet passage.

The invention is illustrated by way of example in the accompanyingdrawings in which Figure 1 is a cross-sectional elevation through a fuelinjection pump unit in which the cylinder sleeve is arranged for bothaxial and rotational 5 movement;

Figure 2 is a fragmentary view to an enlarged scale showing thearrangement of the port groove on the recip-rocatory plunger;

Figure 3 is a development diagram showing 10 the manner in which theports coact, the cylinder sleeve being adjusted to produce a largeinjection;

Figure 4 is a diagram corresponding to Figure 3, the cylinder sleevebeing adjusted to pro- 15 duce a small injection;

Figure 5 is a perspective view of the end of the plunger illustrated inFigures 1 and 2;

Figure 6 is a view corresponding to Figure 5 showing a modifiedconstruction; 20

Figure '7 is a fragmentary sectional elevation showing a modifiedcylinder and plunger assemblyin which the reciprocatory plunger isadapted for angular adjustment to vary the quantity of fuel injected; 725 Figure 8 is an enlarged fragmentary side View of the cylinder sleeveand plunger shown in Figure '7, looking from the left hand side;

Figure 9 is a similar view looking from the right hand side; 30

Figure 10 is a development diagram illustrating the action of the portsshown in Figure '7;

Figure 11 is a fragmentary perspective view of a modified form ofplunger having a pair of diametrically opposite control grooves. 35

The general construction of one form of fuel injection pump according tothe invention is illustrated in Figures 1 and 2, said pump comprising abody III, the lower part of which is arranged to form a casing H for acam shaft 40 I2. As is usual with this form of pump, the cam shaft l2can carry a plurality of cams for operating a series of pumps arrangedside by side, one for each cylinder of the engine, but for simplicityone pump only is illustrated in Fig- 45 ures 1 and 2. A cam 13 formedupon the shaft I2 is adapted to co-operate with a roller 54 carried by atappet 15, the latter being adapted to slide vertically in a tappetguide it, the tappet guides for the whole set of pumps preferably 50being formed as a single detachable unit secured by screws, one of whichis indicated at ll. The upper part of the body It! is bored for thereception of a tubular cylinder casing l8, which latter is normally heldupon its seating I9 by 55 downward pressure exerted upon the flange 29of a delivery valve guide 21 through the medium of a screw-threaded plugmember 22. The dclivery valve is indicated at 23 and is held upon itsseating by a spring 24 in the usual manner; but the lower part of thehousing 2| is extended downwardly to form a stationary plunger 25 boredco-axially at 26 to take the delivery fuel. Disposed between thestationary plunger 25 and the cylinder casing l8 is a sleeve 21 whichserves as a cylinder and is arranged for limited vertical slidingmovement as well as rotational movement for controlling the injection offuel, as will be hereinafter explained. The means used for impartingthese movements to the cylinder sleeve 21 comprise a pair of rack bars28, 29, which engage with rotating members in the form of pinions 39 and3| respectively.

The pinion 30 is screw-threaded internally for engagement with ascrew-thread 32 formed upon the exterior of the cylinder sleeve 21, sothat, assuming this sleeve to be held against rotation, endwise movementof the rack bar 28 will turn the pinion 30, thus moving the sleeve 21either in an upward or a downward direction, since the pinion 30 isanchored against endwise displacement by suitably forming the body witha shoulder, indicated at 33. The pinion 3| serves to locate the cylindersleeve 21 in any desired angular position and for this purpose splines34 are formed down the exterior of the cylinder sleeve 21 and engage thepinion 3|, so that an gular movement imparted to the latter by means ofthe rack bar 29 is correspondingly transferred to the cylinder sleeve21.

Operating within the lower end of the cylinder sleeve 21 is areciprocatory plunger 35 the lower end of which is provided with a head36 engaged by a readily removable washer 31, the latter serving as anabutment for a helical compression spring 38 for returning the plunger35 during the suction stroke. The washer 31 is slotted radially at 39 sothat it can be readily removed by temporarily relieving the pressure ofthe spring 38, thus freeing the lower end of the plunger 35 and enablingthe latter to form part of a readily removable assembly unit comprisingin addition to the plunger, the cylinder sleeve 21, the pinion 30, thecylinder casing I8, and the upper plunger 25, together with theassociated delivery valve guide 2|. It will be observed from Figure 1that by removing the plug member 22 and slacking off a check screw 40,the whole of this unit can be withdrawn in an upward direction forcleaning, replacement, inspection or any other purpose.

The body I is formed with a common longitudinally extending inletpassage 4| communieating through a hole 42 in the cylinder casing l8with a control port 43 formed in the cylinder sleeve 21, while for thepurpose of enabling fuel to flow into and out of the annular space 44around the top of the cylinder sleeve 21 as the latter is adjustedaxially, and also for relieving any pressure which might occur in saidspace 44 due to leakage of fuel past the fixed plunger 25, a passage 45is arranged to communicate with the inlet passage 4|.

As will be seen from Figure 5, the upper end of the plunger 35 is formedwith a helical port groove 46 which opens into the end surface of theplunger 35 for communicating with the working space in the cylindersleeve 21, said groove 46 being adapted to co-operate with a portopening formed in the cylinder sleeve 21, as indicated at 41 (Figs. 3and 4). This port is substantially triangular in shape and is arrangedso that its lower edge 43 lies substantially parallel with the controlling edge 49 of the groove 46, while its upper edge 50 is similarlyparallel with the upper controlling edge of the plunger 35. Thiscontrolling edge is arranged obliquely by cutting away the corner of theplunger, the purpose of this being to compensate for the slight axialmovement of the cylinder sleeve 21 which is caused when the pinion 30 isrotated, with a View to adjusting the amount of fuel. The edge 5|therefore defines a helix having a pitch and direction of progresssimilar to that of the screwthread 32. It will be understod that theplunger and sleeve may be provided with a pair of oppositely disposedhelical grooves, as shown in Figure 11 for the purpose of providing alarge port opening and also equalizing the pressure on the plunger, theposition of such a second groove being indicated at 46a, while thecorresponding controlling edge on the end of the piston is similarlyindicated at 5la. In this case a second inlet passage similar to thepassage 4| can be incorporated in the body In.

The action of the ports is shown clearly in Figures 3 and 4 in which thetop of the plunger 35, as shown in full lines at 52, is in the positioncorresponding to the lowest part of its active stroke for the particularposition of the cylinder port 41. Assuming that the plunger 35 istravelling upwardly, it will be seen that the controlling edge 5| isjust about to complete the closing of the cylinder port 41, andthereafter until the plunger assumes the position indicated in dottedlines at 53, said port 41 is closed by the uncut substantiallytriangular portion 54 of the plunger 35. At the position 53, however,the controlling edge 49 of the groove 46 passes across the edge 48 ofthe port 41, thus opening the working space of the pump to the inletpipe, by way of the groove 46 and so causing the injection of fuel tocease. It will be readily seen that by shaping the port 41 so that itsedges 48 and 50 are parallel respectively with the controlling edges 49and 5|, a comparatively large area of passage for the release ofrejected fuel and a comparatively quick cut-01f are provided, thusavoiding the constricting effect which is produced when a circular portis arranged to slide over a straight or oppositely curved controllingedge, as in fuel injection pumps which have hitherto been proposed.

Figure 4 corresponds to Figure 3 but the cylinder port 41 has been movedto the right by rotation of the pinion 3| (see Figure l), a slightrising movement being also imparted to the cylinder sleeve 21 due to thescrew-thread 32, so that the port 41 in fact follows the slope of thecontrolling edge 5|. In this case it will be seen that injection ceaseswhen the piston reaches the position indicated in broken lines at 55, i.e., when the controlling edge 49 begins to overlap the controlling edge48 of the port 41, the amount of fuel injected being proportional to thedistance a travelled by the plunger 35 as compared with the distance 72shown in Figure 3.

Axial displacement of the cylinder sleeve 21 by rotation of the pinion30 brings about movement of the port 41 in the direction of the arrows cin Figure 3, and it will be seen that this causes the beginning and theend of injection to be advanced or retarded simultaneously and to thesame extent, thus providing a timing control which does not alter thequantity of fuel injected.

As before mentioned, the controlling edge 5| iii on the plunger 35 mustbe of the same hand as the screw-thread 32. The direction of rotation ofthe pinion 30, to produce, say, upward movement of the cylinder sleeve21 may require to be reversed, and in this case a thread of oppositehand would be necessary, the top of the plunger being shaped as shown inFigure 6, due compensation being made in the helix angle of the portgroove 46.

In the arrangement shown diagrammatically in Figure '7, the cylindersleeve 21 instead of being rotated about its axis in order to producevariations in the quantity of fuel injected, is held against rotation bythe engagement of the check screw 40 with a longitudinal slot 56 formedin the end portion at least of said cylinder sleeve 21, thus enabling alimited endwise movement to be imparted to said sleeve by actuation ofthe rack 28 and the pinion 30. The quantity of fuel injected per stroke,however, is regulated by rotational adjustment of the plunger 35, and inthe construction illustrated, said plunger is formed with a diametralpin ladapted to engage in slots 58 formed in a sleeve 59, which latteris attached to or produced in one with the pinion 3|.

A modified port arrangement, which is incorporated in Figure 7 will beseen more clearly by reference to Figures 8 and 9 and to the developmentdiagram (Figure which latter represents the whole circumference of thereciprocatory plunger 35 and the internal surface of the cylinder sleeve21, the ports in the sleeve being shown in full lines and those in theplunger by dotted lines. The end part of the plunger 35 is drilledaxially at 60 and diametrically at 6|, the extremities of the hole 8|being extended to form an inlet groove 62 arranged circumferentially,and a spill-port 63 extending obliquely as shown. At one side thecylinder sleeve is formed with an inlet port 54 communicating with aninlet passage 65 in the body ID (see Figure 7), while at the oppositeside of the cylinder, a spill port 66 is formed obliquely and similarlycommunicates with a spill-passage 61. This construction again providesextensive controlling edges which produce substantial passages almostimmediately after overlapping, but otherwise works in accordance withknown principles.

In the position of the ports shown in Figure 10, the fuel injection isjust about to commence, as the port 62 with its controlling edge 68 isjust passing off the port 64 with its controlling edge 69. Injectionwill thereafter take place until the controlling edge 10 of the port 63reaches the controlling edge H of the port 66, when the pressure in theworking space of the pump will be released by the passage of rejectedfuel downwardly through the bore 60, 6|, through the spill port 66 intothe passageway 61. This passageway can communicate with the inletpassage 65 for conducting the rejected fuel back to the cylinder, oralternatively said rejected fuel may be returned to the usual supplytank. It is found in practice that this construction gives the advantageof allowing the rejected fuel to become de-aerated before passing onceagain into the pump cylinder. Rotational adjustment of the reciprocatoryplunger 35 to the right (as seen in Figure 10) has no effect on thecommencement of injection, as the port 62 is merely moved to a positionindicated at 62a. On the other hand, the port 63 assumes a position 63ain which it requires less vertical movement of the reciprocatory plunger35 before the controlling edge 1E) overlaps the controlling'edge H, thusterminating injection. Axial movement of the cylinder sleeve, say in anupward direction, moves both of the ports 64 and 66 also in an upwarddirection, thus retarding the beginning and the end of injection to anequal extent without altering the quantity of fuel delivered.

It will be understood that the invention is not limited to theconstructions illustrated and the axially adjustable cylinder sleeve andstationary plunger may be used in fuel injection pumps of differentdesign. Moreover it is evident that in the embodiments illustrated, theport arrangement shown in Figures 1 to 6 may be used in conjunction witha plunger which is arranged for rotational adjustment, and in this casethe controlling edge 5| will normally extend circumferentially. Alsowhere the ports shown in Figures 7 and 10 are employed with a cylindersleeve controlled as in Figure 1, the ports 62 and 64 would be arrangedobliquely to compensate for the action of the screw thread 32.

What I claim is:--

1. A fuel injection pump comprising a body formed with a bore, acylinder casing fixedly mounted within but removable from the bore, atubular cylinder mounted within the casing and capable of slidingaxially therein, a one-piecereciprocating plunger closing the lower endof the cylinder, means for reciprocating the plunger, an axially boredfixed plunger extending into the upper end of the cylinder to close thelatter, a one-way delivery valve closing the bore in the fixed plunger,a fuel inlet passage in the body, a port in the cylinder wallcommunicating with said inlet passage, a controlling edge on the plungerdetermining the beginning of fuel injection and another edge thereondetermining the end of injection, means for moving the cylinder axiallyto alter the time of the beginning and the ending of injectionsimultaneously and to the same extent, means for bringing about relativerotation between the reciprocating plunger and the cylinder to vary thequantity of fuel delivered at each stroke, and a passage connecting withthe inlet passage, an annular space embracing the fixed plunger andbounded by the slidably adjustable cylinder, the arrangement being suchthat the cylinder casing when removed from the body carries with it as aunit the cylinder, the fixed plunger and the reciprocating plunger.

2. A fuel injection pump comprising a body formed with a bore, acylinder casing fixedly mounted within but readily removable from saidbore, a tubular cylinder mounted within said casing and slidable axiallytherein, a reciprocating plunger closing the lower end of said cylinder,means for reciprocating said plunger, an axially bored fixed plungerextending into the upper end of the cylinder, the fixed andreciprocating plungers being of equal diameter, and the bore of thecylinder being constant in diameter throughout its length, an outwardradial flange formed in one with the fixed plunger and arranged to bearupon the upper end of the cylinder casing to keep the latter inposition, a plug member screw threaded into the body and bear ing uponsaid outward radial flange, a fuel inlet passage formed in the body, acontrolling edge on the reciprocating plunger arranged to coact with aport in the cylinder to determine the commencement of injection, anotheredge on the reciprocating plunger coacting with an edge on the cylinderto determine the end of injection, means for bringing about relativerotation between the cylinder and the reciprocating plunger to regulatethe quantity of fuel injected at each stroke, means for axially movingthe cylinder within the cylinder casing to change the timing of theinjection without altering the quantity, and a passage connecting withthe inlet passage the space between the upper end of the cylinder andthe outward flange formed upon the fixed plunger.

GEORGE JOSEPH TRAPP.

